Apatite has excellent bioaffinity and can directly be bonded, to a bone tissue. Therefore, the apatite is widely used as a material for an artificial, bone or an artificial dental root. Above all, calcium hydroxyapatite is a main component of a living hard tissue such as a bone or a tooth, and therefore is one of materials most well utilized. Further, it is known that β-tricalcium phosphate (hereinafter referred to as “β-TCP”) is easily absorbed in a bone, and is easily substituted with a new bone alter being embedded in a living body.
On the other hand, it is known that titanium has excellent strength and has low reactivity to a living body, and for this reason, is widely used, as a material for an artificial joint or an artificial dental root (JP-A-63-143057).
It is desirable that after once being embedded in the body, the material for an artificial joint, an artificial dental root, and the like is strongly bonded to a bone tissue, and is united with the bone tissue.
However, titanium has low reactivity to a living body as described above, but on the other hand, has low affinity with a living tissue. Therefore, it was difficult to unite titanium with a hone tissue.
For this reason, it has been conducted to cover a surface of titanium with apatite for the purpose of increasing adaptability of titanium to a bone tissue (for example, JP-A-3-186272).
In this case, however, it has been a current situation that a satisfactory bioadaptability is not obtained.
On the other hand, as other composite material using apatite and titanium, a titanium compound produced by a coprecipitation method is reported (JP-A-2000-327315 and JP-A-2001-302229). The titanium compound is in a form of powder, and a product obtained by sintering this has not been known.
Further, it is known that of inorganic substances, there are some substances to be difficult to sinter the same alone as in β-TCP or the like. It is not known that the inorganic substance is mixed with the titanium compound above, and then sintered.